This invention relates in general to mechanical control elements. More specifically, it relates elements of the type used in mechanical controls for internal combustion engines such as rocker arm assemblies.
Control elements such as in the form of rocker arms and the like have, in the past, been fabricated from inductively hardenable steel. These steel elements are hardened on a contact surface thereof inductively in order to make them more wear-resistant.
It has become advantageous to substitute cast iron for the hardenable steel fabrication material. It is known to produce iron elements cast in a desired shape. The elements are cast from iron with spheroidal graphite which are subjected to heat treatment with austenitic carbonitration, etc. Subsequently, these elements are cooled in such a manner that increased strength of material develops providing enhanced wear and durability. In order to improve the sliding properties of a control surface, the element may be phosphalated. However, the wear-resistance of cast iron elements is often not satisfactory for continuous or long-term operation of the element.